Centrifugal switch



Aug. 2, 1955 Filed Sept. 4, 1944 R. G. FERRIS CENTRIFUGAL SWITCH 3 Sheets-Sheet l INVENTOR ROBERT 6. FE RIP/5 ATTORNEY Aug. 2, 1955 R. G. FERRIS 2,714,640

CENTRIFUGAL SWITCH Filed Sept. 4, 1944 3 Sheefcs-Sheet 3 II III I INVENTOR ROBERT 6. F E RR/S ATTORNEY CENTRIFUGAL SWITCH Robert G. Ferris, Harvard, 111., assignor to the United States of America as represented by the Secretary of the Navy Applicafion September 4, 1944, Serial No. 552,677 10 Qlaims. (Cl. 20080) This invention relates generally to centrifugally operated switching devices for use in rotary projectiles of that class which incorporates electrically-operable firing means, and more particularly concerns an improved unshorting and self-destruction switch therefor.

One of the principal objects of the invention is to provide an extremely simple device of the character indicated which upon firing of a projectile containing it will automatically break a short circuit normally maintained across the electrically operable primer of such projectile, the firing means of the projectile being thus positively maintained in safe condition until the time of firing, and then armed.

Another object of the invention is to provide such a switch which utilizes a conductive liquid, such as mercury, and which is so constructed as inherently to tend to maintain its dynamic balance, and accordingly to maintain the dynamic balance of the projectile.

Another object of the invention is to provide, in combination with such an unshorter, novel self-destruction means which, upon predetermined decrease of spin of the projectile, will act electrically to destroy the projectile.

Still another object is to provide a circuit controlling device of the character indicated which is so arranged that the mercury employed may be introduced while the switch is spinning in a centrifuge or other rotary means, at the speed at which self-destruction is desired, thereby insuring accurate introduction of the right amount of mercury to assure the desired action.

Further objects of the invention, not mentioned hereinabove, will be evident upon consideration of this disclosure in its entirety.

In the drawings:

Fig. 1 is a vertical diametric cross sectional view of a circuit unshorting device incorporating the principles of the present invention;

Fig. 2 is a plan view of the embodiment shown in Fig. 1;

Fig. 3 is a sectional view smiilar to Fig. 1, showing the invention in a modified form which embodies both selfdestruction and unshorting features;

Fig. 4 is a horizontal sectional view of the modification of Fig. 3, taken substantially on the plane indicated by the line 4- of Fig. 3 and looking in the direction of the arrows;

Fig. 5 is a sectional detail taken substantially on the plane indicated by the line 55 of Fig. 4 and looking in the direction of the arrows;

Fig. 6 is a sectional view similar to Fig. 1 showing another modified form of the invention;

Fig. 7 is a horizontal sectional view taken substantially on the plane indicated by the line 7-7 of Fig. 6 and looking in the direction of the arrows;

Fig. 8 is a vertical sectional view showing still another embodiment of the invention; and

Fig. 9 is a wiring diagram.

The embodiment shown in Fig. 1 comprises a hollow cylindrical casing 10 formed entirely of metal or other electrically conductive material except for the insulating rings 14 by which a circular central section 12, 13 of each end wall is insulated from the remainder of the casing. Within the casing 16 is a supply of mercury 15 sufficient to fill the housing about one-half full. The discs 12, 13 may be electrically connected to one another, as indicated at 16, and the supply of mercury is sufiicient to'connect either or both of the discs 12 and 13 with some part of the main casing portion 11 at all times and when the housing is in any position, except when it is revolving about the axis of the cylinder above a certain limiting speed.

In use, the device is mounted in a projectile (not shown) in coaxial disposition. Electric connections are run from the discs 12 and 13 and from the circular outer casing portion 11 respectively to the electrically operable primer S, so that normally a short circuit will exist across the squib or primer, preventing premature detonation thereof in the event premature operation of the remainder of the fuze mchanism should take place.

When the projectile is fired and setback has decreased, centrifugal force will throw the mercury outwardly with in portion 11 until it occupies an annular space entirely therewithin and clear of the discs 12, 13. The inner limits of the body of mercury at such time are shown in dotted lines at X in Fig. l.

The circuit across the squib is broken as a result of this shift of the mercury, arming the fuze so that detonation may take place when operation of the fuze mechanism is induced by a target. If centrifugal force diminishes, as in the event that the projectile fails to find a target and its force is spent, the mercury will fall away from its peripheral position and again short circuit the discs to portion 11, with the result that the projectile will be returned to safe condition.

In the modification shown in Figs. 3 and 4 of the drawings the casing 2% is a hollow sheet metal annulus including a top wall 21, a bottom wall 22 and inner and outer walls 23, 24. An insulating ring 25 surrounds the inner wall 23 within the casing, and fitted about the ring 26 and insulated thereby from the casing is a conductor ring 27. Formed in the inner wall 23 near the bottom wall 22 and communicating with the interior of the casing are radial openings 25. Mounted in two of the openings 25 are bushings or grommets 25a, of insulating material thru which the conductors 27b, 2% are led, the grommets being sealed with respect to the conductors as well as with respect to the openings 25 in which they are fitted. One of the radial openings, as 25, is provided with a simple plug and serves as a filler hole for mercury, as will appear.

Shiftably mounted in the casing 20 between the walls 21 and 22 thereof is a dividing ring 28, which may be formed of non-conductive plastic. Embedded in ring 28 is a circular, conductive contact ring 29, which may be of copper. The ring 23 is cut away at points spaced about its circumference as indicated at 3 3 to expose portions of the contact ring 29, and also to provide radial passages through the ring assembly.

Also within the casing 2t: and lying adjacent the inner surface of the outer wall 24 is a resilient ring 31 of cellular neoprene or the like. A quantity of mercury 32 is contained in the casing 2t and, as will be explained more fully hereinafter, may be placed therein while the casing is revolving at a high speed.

This embodiment of the invention is adapted for use as an unshotter and also as a self-destruction switch. It is installed coaxially in a projectile, rings 27, 29 being connected across the primer and the quantity of mercury within the casing being sufiicient to maintain a shortcircuiting connection between such rings at all times except when the assembly is rotating about its axis at or above a certain speed. Upon firming and resultant rotation of the projectile and contained assembly, centrifugal force will cause the circuit across the primer to be broken, arming the same for firing by the fuze mechanism. In addition, the device is employed to connect a firing condenser directly with the primer, to fire the projectile after the rate of spin thereof has decreased to a relatively low level. The electrical connections for the embodiment of the invention above described, as well as for those of Figs. 7 and 8 are shown in Fig. 9. The plate of the Thyratron or equivalent discharge tube T is connected, through the insulating bushing in one of the openings 25, to the ring 29. The conductor ring 27 is connected to the positive B battery terminal Bl, and the case is connected to the ground, which is usually constituted by the can of the projectile.

The supply of mercury 32 is sufiicient to connect both of the rings 27, 29 with the casing, as stated, at all times except when the casing is rotated rapidly. It will be seen that when the projectile is at rest the plate of tube T will be grounded, and the primer S short circuited. When the mercury is spun outwardly within the casing during flight of the projectile, however, the connection between the ground and the ring 27 is immediately broken, interrupting the short circuit across the primer. Continued spinning causes the mercury to move through the openings 30 into the annular space outside ring 28. Ring 31 is compressed by the mercury and the connection between the bared portions of the ring 29 and the ground is broken. This breaks the short circuit from the thyratron plate to the ground and the projectile may then be detonated, upon operation of the electric circuits (not shown) within the fuze.

In the event the projectile is not detonated by the fuze, self-destruction occurs as soon as the spin of the projectile diminishes to such degree that the mercury is forced inwardly by the expansion of the compressed air in the cells of the neoprene ring 31 to complete a circuit between the ring 29 and the casing. When this takes place, the firing condenser will be connected directly across the primer to fire it and destroy the projectile. The B current supply is such that it is activated only after the projectile is fired. Various means are known in the art for accomplishing this, and accordingly need not be described here, but it will be noted that by reason of this fact, the firing condenser is not charged until after discharge of the projectile from the gun.

The ring 28 is movably mounted in the casing and the quantity of mercury is sufiicient to center the ring 28 which therefore floats in accordance with the spin of the projectile. Thus the mercury will be properly distributed and the contacts properly closed even though the projectile spins off center.

The casing of the embodiment of Figs. 6 and 7 is designated 20A and consists of a pair of partially interfitted or nested channeled rings 21A, 22A, forming a hollow annular chamber analogous to that of the embodiment last described. The margins of easing sections 21A, 22A are welded or otherwise suitably secured to each other to seal the chamber.

An outwardly opening insulating channeled ring 28A is movably mounted in the chamber and carries upon its inner periphery the contact element 29A. An inner contact element or ring 27A is supported similarly to the ring 27 of the last described embodiment, upon the inner wall of the casing and the contact elements 27A, 29A are electrically connected in circuit by conductors as 42, projected through and sealed in the insulating bushings A mounted in the inner wall of the casing. A similar opening, normally plugged, also serves as a charging hole for mercury.

In this embodiment of the invention the outward movement of the mercury, when the device is spun, displaces the air in the enclosed space surrounding the annular channel 28A, filling the entire space outside the annulus except for such air as is entrapped in the bottom of the channel. Such air is compressed by the transmitted pressure and acts as a spring. With decrease in spin, the expansion of such air drives a portion of the mercury inwardly about the free edges of the annulus and into electrical contact with element 29A, closing the self-destruction circuit between this element and the casing. It will be understood that when the projectile is initially spun mercury will be shifted away from the contact ring 27A fitted about and insulated from the inner wall of the ring 22A, to break the short circuit across the primer, as in the embodiment last described.

In the embodiment of Fig. 8 external means is employed for returning the mercury to the self-destruction position, upon decrease of spin of the projectile. The casing 20B is provided with a contact ring 27B similar to the contact band or ring 27 of the second described embodiment. A movable ring or annulus 28B is also similarly mounted in the casing and formed with openings 30B and a conductive core 29B spaced portions of which core are exposed by the openings.

Mounted on the top wall of the casing 20B near its periphery is a housing 50 containing a bellows 51 communicating at its open lower end with the interior of the casing. The bellows is biased to compressed condition by a coil spring 52 confined in the housing 50 above the bellows.

In so far as the unshorting feature is concerned, the operation of this form of the invention is identical with that of the embodiments of Figs. 3 to 7. When the mercury is spun outwardly by centrifugal force, however, it also flows upwardly into the bellows 51 and expands the latter against the pressure of spring 52. In event the projectile is not detonated by a target, diminution of centrifugal force results in compression of the bellows by spring 52, which ejects the mercury and forces it inwardly to such extent that it again bridges and connects ring 29B and the casing, closing the self destruction circuit.

By reason of the radial arrangement of the filler holes at the inner peripheries of the annular embodiments of my invention, the mercury may be introduced while the device is spinning in a centrifuge, as through an axially disposed tube 35 having a radial arm 36 projecting into one of the radial openings as 25, the indicated accessory filling means 35, 36 being indicated in dotted lines in Fig. 3. It is thus possible to insure introduction of the proper amount of mercury for effective operation.

A time lag may be introduced by restricting the size of the openings or passages through the ring 28 (or 28A or 28B). The flow of mercury into the outer compartment of the casing may thus be delayed so that the short circuit across the squib will not be broken until after the expiration of a predetermined time.

I claim:

1. A switching device comprising a substantially symmetrical metallic casing mounted to rotate about an axis of symmetry, said casing comprising axially opposed portions of conductive material, an annular portion of conductive material surrounding the axial portions and rings of insulating material connecting the said portions, and a quantity of conductive fluid within the casing which will be caused to flow outwardly by centrifugal force upon sufificiently rapid rotation of the casing for uncovering the axial portion of the casing and opening an electric circuit, said conductive fiuid being caused by gravitation to flow to overlie said annular portion and at least one of said axial portions when said casing is at rest, for closing said electric circuit regardless of the attitude of said casing.

2. A switching device as recited in claim 1 including an annular cellular member within the casing and compressiblc by the conductive fluid under centrifugal force to permit disengagement of said fluid from the axial portions, for breaking the short circuit existing between the annular portion and said axial portions.

3. A switching device of the class described including, a substantially symmetrical hollow metallic casing mounted to rotate about an axis of symmetry, a dividing ring of insulating material shiftably mounted within the casing, a ring of conductive material embedded in the dividing ring, said dividing ring having substantially radially extending grooves cut away at points spaced about its periphery to expose portions of said ring of conductive material to define contact surfaces, a contact mounted within the casing near the axis thereof and insulated from said casing, and a body of conductive fluid within the casing and normally bridging at least one of the exposed surfaces of the ring of conductive material with the contact for etfecting an electrical short circuit, said fluid being caused to flow outwardly upon rotation of the casing for exposing said contact and breaking said electrical short circuit.

4. A switching device, comprising, a substantially symmetrical casing mounted to rotate about an axis of symmetry, electrically conductive contact portions within said casing and insulated from one another, at least one of said contact portions being located substantially centrally of said casing and another of said contact portions being spaced outwardly of said centrally located contact portion, a ring having radial ports therethrough and frictionally mounted in said casing to be driftable radially, and a quantity of conductive fluid within the casing for providing electrical connection between said contact portions when the casing is at rest, said fluid being caused to flow outwardly upon rotation of the casing for exposing said contact portions and breaking said electrical connection.

5. The arrangement as set forth in claim 4, with additionally, means compressible by the outward movement of said conductive fluid to permit the disruption of said electrical connection when the rate of rotation exceeds a predetermined value and to return said conductive fluid to re-establish said electrical connection when the rate of rotation falls below said predetermined value.

6. The arrangement as set forth in claim 5, wherein, the compressible means comprises a resilient annular cellular member mounted within said casing adjacent the outer peripheral wall thereof.

7. The arrangement as set forth in claim 5, wherein, the compressible means comprises a bellows normally spring biased to compressed condition and communicating with the interior of said casing adjacent the outer periphery thereof.

8. A switching device, comprising, a substantially symmetrical casing mounted to rotate about an axis of symmetry, a quantity of conductive fluid within said casing and movable outwardly in response to centrifugal force upon rotation of said casing, a plurality of radially spaced contact means within said casing and insulated from each other, one of said contact means being located centrally of said casing and another of said contact means being spaced outwardly of said centrally located contact means, said second mentioned contact means including an annular body of conductive material loosely mounted to be driftable radially in said casing, said conductive fluid normally short circuiting said contact means when the casing is at rest, the quantity of fluid being such that the fiuid will move out of engagement with at least one of said contact means to break said short circuit when the casing is rotated at a suflicient rate.

9. An arrangement as set forth in claim 8, with additionally, a resilient annular cellular member mounted within said casing adjacent the outer peripheral wall thereof, so that the outward movement of the conductive fluid will compress said cellular member and disrupt the short circuit when the rate of rotation of the casing exceeds a predetermined value and be returned by said cellular member to re-establish said short circuit when the rate of rotation falls below said predetermined value.

10. An arrangement as set forth in claim 8, with additionally, a bellows normally spring biased to compressed condition and communicating with the interior of the casing adjacent the outer periphery thereof, so that the outward movement of the conductive fluid will compress said cellular member and disrupt the short circuit when the rate of rotation of the casing exceeds a predetermined value and be returned by said cellular member to reestablish said short circuit when the rate of rotation falls below said predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS Re. 8,102 Weston Feb. 26, 1878 196,846 Weston et al. Nov. 6, 1877 949,859 Swift Feb. 22, 1910 1,917,581 Gillen July 11, 1933 1,983,502 Vaughan Dec. 4, 1934 2,301,217 Lambert Nov. 10, 1942 FOREIGN PATENTS 213,735 Germany Sept. 22, 1909 

